Effects of positive end-expiratory pressure on the work of breathing in adult respiratory distress syndrome patients

In 10 sedated, paralyzed, mechanically ventilated adult respiratory distress syndrome patients we measured the inspiratory mechanical work done on the respiratory system (Wi,rs). We used the technique of rapid airway occlusion during constant flow inflation to partition Wi,rs into static work (including work due to intrinsic positive end-expiratory pressure [PEEPi]) and dynamic work due to airway resistance and viscoelastic forces within the respiratory tissues. The measurements were carried out at four levels of PEEP (0, 5, 10, 15 cm H20). Without PEEP, Wi,rs was threefold greater than in normal subjects. With PEEP, Wi,rs decreased slightly as a result of a significant decrease of the static work due to PEEN. The high values of Wi,rs observed in our adult respiratory distress syndrome patients would likely cause inspiratory muscle fatigue during spontaneous breathing, hence necessitating mechanical support.